Utility trench and trench system

ABSTRACT

Incompatible utility lines such as power, gas and telephone lines serving urban and suburban businesses and residences are layed in separate parallel compartments of a utility trench system made up of a plurality of trench sections butted together in end-to-end relation. Each of the trench sections comprises a structure having a horizontally disposed base and upended side walls defining a trench with a bottom wall between them. The trench may be divided into two or more open topped parallel compartments by dividers running parallel to the side walls and having a height approximately that of the side walls. Open-ended channels are formed in the base directly beneath the bottom wall of the trench, the channels extending transverse to the length dimension of the trench. Knockout portions are formed in the bottom wall of each of the compartments, the knockouts defining openings through which cable layed in each of the compartments can exit the structure without crossover or chance of direct contact with other lines layed in an adjoining compartment. A removable top whose upper surface may serve as a sidewalk seats upon the upper edges of the side walls.

United States Patent [191 Schille et a1.

1 41 UTILITY TRENCH AND TRENCH SYSTEM [75] Inventors: Samuel C. Schille, Kent; John B.

Schack, Auburn, both of Wash.

[73] Assignee: Concrete Conduit Company, Inc., Auburn, Wash.

22 Filed: Dec. 4, 1970 211 Appl. No.: 95,010

52 user ..52/l00,52/169,52/221,

138/105, 174/39 511 1111.01 1102;; 9/06 [58] Field of Search ..94/1,2629,

Primary Examiner-John E. Murtagh [5 7 ABSTRACT Incompatible utility lines such as power, gas and telephone lines serving urban and suburban businesses and residences'are layed in separate parallel compartments of a utility trench system made up of a plurality of trench sections butted together in end-to-end relation. Each of the trench sections comprises a structure having a horizontally disposed base and upended side walls defining a trench with a bottom wall between them. The trench may be divided into two or more open topped parallel compartments by dividers running parallel to the side walls and having a height approximately that 0f the side walls. Open-ended channels are formed in the base directly beneath the bottom wall of the trench, the channels extending transverse to the length dimension of the trench. Knockout portions. are formed in the bottom wall of each of the compartments, the knockouts defining openings through which cable layed in each of the compartments can exit the structure without crossover or chance of direct contact with other lines layed in an adjoining compartment. A removable top whose upper surface may serve as a sidewalk seats upon the upper edges of the side walls.

10 Claims, 7 Drawing Figures PAIENTEllJuu 1 I am INVENTOR. SAMUEL c. SOHILLE BY JOHN B. SGHACK UTILITY TRENCI-I AND TRENCII SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a utility trench and trench system wherein the top surface of the trench may be used as a sidewalk.

2. Prior Art Relating to the Disclosure Many urban and suburban communities in new and existing subdivisions are now serviced by underground utilities including electric power, telephone and TV cables, natural gas or oil lines, etc. The utility companies in most instances work completely independently of one another and install their respective cables or lines at different times and at different locations. This lack of coordination results in. repeated digging of trenches to house the respective utilities with the always present probability that an already layed cable or line will be dug into by the utility company or contractor installing a further utility cable or utility line. Undergrounding of, particularly power cable, is expensive because of the type of insulating cable which must be used. Power cable for undergrounding purposes in most urban and suburban areas, for example, must be impervious to water and dampness, corrosion-resistant, rodent proof and resistant to penetration by instruments. commonly used in excavation. Underground power cables have been used in densely populated business areas of larger cities, the power cables usually trained through ducts which are extended through tunnels a substantial distance below the street surface with access to the tunnels provided by manholes at spaced intervals. Depending on the size cable used adequate ventilation for purposes of heat dissipation is a problem when the power cables are trained through ducts.

Trench systems for underground cables, pipe lines, etc. are known and disclosed in US. Pat. No. 1,017,759 and US. Pat. No. 2,862,367. These trench systems, however, provide no way for separately conveying utility cables or utility lines which are incompatible with each other such as, for example, electric power cable and telephone cable. Incompatability has reference to those utility lines which, for safety reasons and continuedpower maintainance must not be layed in contact with each other or closely adjacent each other such that disruption of one line or cable would result in breaking, short circuiting or otherwise disrupting the service of one or more of the remaining utility lines and cables.

SUMMARY OF THE INVENTION This invention relates to a utility system for conveying more than one incompatible utility cable or line in a trench 'system'having removable top covers whose upper surface may be'used as a sidewalk. The trench system is made up of a plurality of open-topped trench sections, preferably of precast reinforced concrete butted together in end-to-end relation, the sections having removable top portions resting on the trench section's whose upper surface may serve as a sidewalk. The trench formed by the upended sidewalls of each section may be divided into two or more separate parallel compartments for laying cable, pipeline or utility line therein, the compartments separated by removable or integral dividing means. Channels formed in the base of each of the sections directly beneath the bottom wall of the compartments run transversely to the length dimension of the compartments and extend the full width of the structure. These channels allow the utility lines to be run to service locations such as residences, business establishments, etc., the cables or lines exiting from the compartments through knockout portions in the bottom walls of each of the compartments. Each knockout portion communicates with a separate transverse channel such that each of the utility lines layed in the respective compartments can exit through its own channel without crossover or contact with an adjacent utility line layed in an ajoining compartment. A removable top whose upper surface serves as a sidewalk fits over the trench section and is retained against horizontal or transverse movement by suitable means. The trench sections are preferably keyed together to prevent lateral or vertical movement of the sections relative to each other when layed in a relatively shallow excavation. The-trench system is particularly useful in urban and suburban residential and commercial areas when layed adjacent to and parallel to the streets.

It is a primary object of this invention to provide a compartmented trench system in which incompatible utility lines, such as power and telephone cable, can be layed without danger of interference by one with the other.

It is a further object of this invention to provide a utility trench system made up of individual trench sections butted together in end-to-end relation having ready access thereto by means of removable top sections whose upper surfaces serve as a sidewalk.

It is a further object of this invention to provide economical and practical means of undergrounding utility lines without the necessity of employing expensive cable.

It is a further object ofthis invention to provide a utility trench system which is essentially maintainance free.

It is a further object of this invention to provide a utility trench system wherein the cost thereof can be shared by participating utility companies.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a trench section and corner sectionwith the tops thereof removed;

FIG. 2 is a plan view of two trench sections and a corner'section butted together with the tops removed illustrating one way in which utility lines can be layed and exited at various locations;

FIG. 3 is a plan view of one section of the trench structure shown in FIG. 1;

FIG. 4 is a side elevational view with parts broken away of the trench structure of FIG. 3;

FIG. 5 is a cross sectional view along section line 55 of FIG. 3;

FIG. 6 is a partial cross sectional view along section lines 6-6 of FIG. 3; and

FIG. 7 is an isometric view of a modified utility. trench with the top and removable slab positioned therein removed.

DETAILED DESCRIPTION OF THE INVENTION The utility trench system of this invention is made up of a number of individual trench sections layed in endto-end relation in a relatively shallow excavation on a suitable base such as compacted sand adjacent a paved street or other suitable location. The removable tops of the trench sections have upper surfaces suitable as a sidewalk. The individual trench sections are shown in the drawings as being substantially rectangular but this is exemplary only. The configuration of the individual trench sections can be made different from that shown and still employ the basic concepts embodied herein. Preferably each of the trench sections is reversible so that either end of the trench section may be layed in the excavation.

FIG. 1 and FIGS. 3 to 6 illustrate one design of the trench sections of this invention. Each trench section comprises an integral open-topped structure having a horizontally disposed base portion 10 and upended side walls'll and 12 defining between the side walls an open-topped trench. The trench is preferably divided into two or more parallel compartments 23 and 24 by an integral or removable divider 13 running lengthwise and parallel to the sidewalls l1 and 12. The bottom wall 14 of the trench and compartments is integral with the base portion 10 and intersects the respective sidewalls 11 and 12. Directly beneath the bottom wall of the trench and preferably at each end of the trench section are formed channels 15, 16, 17 and 18 extending transverse to the length dimension of the compartments. The channels may be open at either or both ends. Each of the channels is of a sufficient size for a conventional cable or utility line to be extended therethrough. Preferably the channels are located at each end of the individual sections as shown in FIG. 3. Access to the respective channels from the parallel compartments is through knockout portions 19, 20, 21 and 22, the knockout portions formed in the bottom wall of each of thecompartments above the respective channels. The number of channels formed in each end of the trench section generally corresponds to the number of parallel compartments. The knockout portions in the bottom wall of each compartment each communicate with a separate channel so that, on exit of incompatible utility lines from different compartments, there is no chance of crossover or direct contact thereof. For example, referring to FIG. 1, a telephone cable 25 is layed in compartment 24 and exits through an opening formed by knockout portion 22 into channel 18 and out the trench system at essentially a right angle. A power cable 26 in the ajoining compartment 23 exits through an opening formed by knockout portion 19 into channel and out of the trench system at essentially a right angle to the length dimension of the trench system. There'is no possibility of direct contact or crossover of the incompatible utility lines on exit from the trench system.

Between the open-ended channels 15, 16, 17and 18 is a hollow area 27, mainly for weight saving purposes. However, if other utility lines intersect the utility trench they can be extended through the hollow area by knocking out one or more of the skirts 28 and 29 formed in the sidewalls l1 and 12 and covering the hollow area 27. A knockout portion may be formed in the a bottom wall just above hollow area 27 for exit of utility layed in an excavation and covered.

Each of the trench sections includes a removable top 30 whose upper surface 31 serves as a sidewalk. Preferably the top 30 overlaps the width of each of the trench sections so that existing lawn or pavement need not be disturbed when the top is removed for access to the utility lines layed therein. The top includes on its under surface ribs 32, '33 and 34 extending parallel to the length dimension of the trench section. Ribs 32 and 33 are positioned to rest on the upper edges of side walls 11 and 12. Rib 34 is positioned directly above the upper edge of divider 13. Projections 35, 35a, 36 and 36a integral with ribs 32 and 33 overlap the upper edges of side walls 11 and 12 and prevent lateral movement of the top when positioned in place. Preferably the upper edges of each of the side walls 11 and 12 include notches 37 and 38 adapted to receive complimentary projections 37a and 38a integrally formed on each of the ribs 32 and 33, the interaction of the projections and notches preventing longitudinal movement of the top when positioned in place. Projections 39a and complimentary recesses 39b may be formed in each end of the top 30, the projections 39a adapted to fit into recess 39b of an adjoining top section. As shown in FIG. 5 the upper surface 31 of the top 30 may be slightly sloped for drainage purposes.

The height of divider 13 is slightly less than the height of side walls 1 1 and 12, thus the middle rib 34 integrally formed in the top 30 does not normally contact the upper edge of divider 13. Preferably there is a clearance of 1/32 inch to l/l6 inch provided between the lower edge of rib 34 and the upper edge of divider 13. Sidewalls 11 and 12 serve as supporting members for top 30. When unusually heavy loads are exerted on the top due to heavy vehicles or other objects the top deflects and the lower edges of rib 34 will contact the upper edge of divider 13 preventing collapse of the top. The side walls and divider 13 are designed to support any foreseable weight or force which may be exerted on the trench system.

At each end of each of the trench sections are integrally formed recesses 39, 40, 41 and 42 and projections 43, 44,45 and 46. The projections or shear keys are adapted to fit into the recesses or an adjoining trench section and prevent lateral movement of the trench sections relative to each other when layed endto-end. As shown in FIG. 3 the projections 43 and 44 areadapted to fit into recesses of an adjacent trench sections as are the projections 45 and 46. Preferably the projections and recesses are formed a slight distance above the lower surface of the base of the trench sections so that when they are being layed in place the recesses will not be filled with dirt or sand.

A modified trench section is shown in FIG. 7 and includes a horizontally disposed base portion having upended side walls 51 and 52. Transverse channels 53, 54, 55 and 56 are formed in the base portion of the section and extend transverse to the length dimension of the section. At the ends of each of the channels are knockout portions 57, 58, 59 and 60. A planar slab 61 having one or more integral dividers 62 rests between the side walls of the trench section and forms the bottom wall of the trench in which the utility lines or cables are layed. Divider 62 extends parallel to the side walls of the trench section and has a height slightly less than the height of the side walls. The divider divides the trench into two or more para-lel compartments. Knockout portions 63, 64, 65 and 66 are formed in the planar slab (bottom wall of each of the compartments) and are positioned to communicate with separate channels. The knockout portions at each end of the planar slab are offset so that, on exit of utility lines in adjoining compartments, there is no danger of contact or crossover. The removable top of the trench section shown in FIG. 7 is essentially the same as described previously with reference to FIG. 1 and FIGS. 3 to 6.

As shown in FlG. 1 a special type of compartmented trench may be used atcorners or when one trench system intersects another. Rather than use the corner structure shown in FIG. 1 a utility vault of a type similar to that shown and described in US. Pat. No. 3,263,278 may be used or other such structure. The corner structures include a horizontally disposed base 70, upended sidewalls 71, 72 and 73 and corner wall 74. One end of the corner trench is left open and is butted against the end of the trench section earlier described as shown in FIG. 1. The bottom wall or base 70 ofthe corner structure includes an integrally formed divider 75 having a height approximating the height of the sidewalls of channels 15, 16, 17 and 18. Wedge-shaped supports 76 (only one shown) are formed at each of the lower corners of the comer structure for supporting a planar slab 77 of substantially the same dimensions as the bottom wall. The planar slab 77 includes an integral divider 78 dividing the planer slab into two compartments. The planer slab has knockout portions 79 and 80 included therein forpassage of utility cables therethrough. The sidewalls of the corner structure also have knockout portions 81, 82, 83 84, 85 and 86 therein for passage of cables or line therethrough. As many knockout portions may be provided in both the planar slab and sidewalls of the corner structure as needed. The corner structure is provided with a removable top 87 having integral ribs 88 on the lower planar surface thereof adapted to rest on the upper edges of the sidewalls of the corner structure. Rib 89 normally does not contact divider 78 except when an unusually high vertical force component exerted gainst top 87 deflects the top.

Reference is made to FIG. 2 showing a plurality of utility cables, such as power cable and telephone cable, layed in two separate parallel compartments, the cables exiting through respective knockout portions in the bottom walls of each of the compartments and the corner structure. For example, power cable 95 extends through the length of the trench section 90, turns as it extends through corner structure 92 and continues on through trench section 91. Power cable 96 extends through trench section 90 into corner structure 92 and exits to the left through knockout portion 80 into the bottom chamber of the corner structure and then out through knockout portion 82. A telephone cable 97 extends through trench section 90 into corner structure 92 where it exits through knockout opening 79 in the corner structure into the lower compartment thereof and then out through knockout opening 84. There is no possibility of direct contact of the telephone and power cables.

The trench sections of this invention are preferably manufactured from reinforced precast concrete although other materials may be used if desired. Preferably the knockout portions leading to the individual transverse channels are positioned at no more than six foot intervals apart. The trench system is installed by excavating a trench along the area where the utility lines are'to be layed, the depth of the trench ranging from 2% to 3 feet. A compacted base of 3 to 12 inches sand, pea gravel, or finely crushed rock is generally required at the bottom of the excavation to furnish a firm sub-base on which the trench sections are layed. The trench sections are then layed in end-to-end relation and keyed together. Since the individual trench sections are reversible it does not matter which end of the section is inserted into the trench. After the trench system is installed the cables or utility lines are layed in the respective compartments. The cables or lines may exit from the trench system at any desired point by knocking out one or more of the knockout portions and exiting the respective cable through a separate transverse channel. The cable may exit from its particular compartment into the transverse channel and extend in either direction without interrupting either the bed of ground on which the trench sections rest or interrupting another utility line. If desired more than one utility line can be layed in one compartment of the trench as long as they are compatible with each other. For example, a TV cable and telephone cable could be layed side-by-side in one compartment and an electricl power cable in a separate compartment. Although the drawings show only two compartments, more parallel compartments can be provided if desired by further partitioning the trench. If the trench system receives water through gaps between the removable top sections drains may be connected to the knockout portions and transverse channels at spaced intervals to drain the water. Each trench section includes shear keys in each of the end walls to insure correct placement thereof and prevent shift laterlly or vertically, thus maintaining a constant sidewalk level. The trench system is inherently rodent proof, prevents interruption of utility lines by persons excavating for other purposes, and provides complete and easy maintainance of the entire utility system. Electric cable can be used without shielding against dig-in or rodents. Electric cable has better ventilation and heat dissipation when layed in the trench system of this invention than when channeled through ducts as has been previously done. The power cable used may be of a less expensive type than generally required for underground power cable. The top sections resting atop the upper edges of the side walls of each of the trench sections can be removed along any portion of the section for laying additional utility. lines, repairing the lines or for other purposes.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A utility trench system for undergrounding incompatible utility lines which, for safety reasons and continued power maintenance, must not be laid in contact with each other or closely adjacent each other such that disruption of one line would result in breaking, short circuiting or otherwise disrupting the service of one or more of the remaining lines, comprising:

a trench excavation in the ground,

a plurality of elongated one-piece trench sections of precast concrete buried in the trench excavation and butted together in end-to-end relation forming a continuous length of open top side-by-side parallel raceways in which the incompatible utility lines are laid, with exit of the utility lines from one raceway to service locations available at intermittent points along the raceway through the bottom thereof without crossover or chance of contact with utility lines laid in the adjoining raceway, each trench section including (1) a base, (2) upright sidewalls integral with the base having their upper edges exposed at about ground level, (3) key means on the respective ends of each section for locking the ends of like trench sections together to prevent lateral and vertical shift relative to'one another, (4) divider means of precast concrete mounted in the base dividing the trench into two separate side-by-side raceways for different utility lines, (5) two lateral passageways completely traversing the-base at locations spaced longitudinally thereof and (6) knockout access'means, one providing access for a utility line from one of the raceways to only one of the lateral passageways and the other providing access for a utility line from the other of the raceways to only'the other of the lateral passageways; v plurality of vertically removable, elongated cover sections of precast concretehaving substantially planar upper surfaces forming a continuous walkway, the cover sections butted together in end-toe-nd relation and resting on the upper edges of the upright sidewalls of the trench sections, each cover section further having -(1) longitudinal sides projectinga minor portion of their width laterally beyond the upright side walls of the trench sections and interfitting therewith to laterally position the cover sections, and (2) a longitudinal center portion cooperating with the divider means of the trench sections toseparate the raceways and provide center support. 2. The trench system of claim 1 wherein each of the divider means of the trench sections provides support for the center portion of each cover when there is center deflection of the cover section responsive to unusually heavy loads.

3. The trench system of claim 1 wherein each of the cover sections has three longitudinal ribs extending the length dimension thereof on the under surface, two of which rest on the upper edges of the upright side walls of the trench sections and the other of which cooperates with the divider means of the trench section.

4. The trench system of claim 1 wherein the divider means of each trench section is integral with the base.

5. The trench system of claim 1 wherein each of the lateral passageways of each trench section is adjacent to an end of the trench section, wherein the major part of the length of the base other than that occupied by the lateral passageways is of substantially reduced thickness, and wherein each trench section includes ground engaging side skirts extending downwardly from the upright side walls preventing settling of. soil into the areas of reduced thickness after installation of the trench sections into the excavation.

6. A utilitytrench system for undergrounding incompatible utility lines which, for safety reasons and continued power and maintenance, must not be laid in contact with each other or closely adjacent one another upperedges thereof exposed, the ground engaging skirts preventing settling of soil into the hollow area after installation of the base member in the excavation,

upright longitudinally extending side walls and a longitudinally extending upright divider separating the space between the side walls into side-by-side raceways,

respective transverse passageways extending the full width of each foot,

knockout access means, one providing access for a utility line from one of the raceways to only one of the transverse passageways and the other providing access for a utility line from the other of said raceways to only the other of the transverse passageways, and

a vertically removable, elongated cover section of precast concrete having a planar upper surface functioning as a sidewalk and resting onthe upper edges of the side walls, the longitudinal sides of the cover section projecting a minor portion of their width laterally beyond the upright side walls of the base member and interfitting therewith to laterally position the cover section, the cover section also having a longitudinally extending center portion cooperating with the divider means 'of the base member to separate the raceways and provide center support.

7. The utility trench system of claim 6 wherein the cover section has three longitudinally extending ribs on the under surface thereof, two of which rest on the upper edges of the side walls of the base member and the other of which cooperates with the divider means.

8. The trench system of claim 6 wherein the top edges of the side walls of the base member include notches and wherein the longitudinal ribs of the cover section resting on the side walls have complementary integrally formed projections interfitting with the notches in the side walls preventing longitudinal movement of the cover section when in place.

9. A utility trench system for undergrounding utility lines which, for safety reasons and continued power maintenance, must not be laid in contact with each other or closely adjacent each other such that disruption of .one line would result in breaking, short circuiting or otherwise disrupting the service of one or more of the remaining utility lines, comprising:

a trench excavation in the ground,

a plurality of elongated one-piece trench sections of precast concrete butted together in end-to-end relation forming continuous parallel raceways in which the incompatible utility lines are laid, with exit of the utility lines in each raceway to service locations available at intermittent points along the raceway through the base of the trench section without crossover or chance of contact with utility lines laid in the adjoining raceway, each trench section including (1) an elongated, onepiece base member of precast concrete having transversefeet at each end and having a hollow portion between the transverse feet, (2) ground engaging side skirts between each of the feet preventing settling of the soil into the hollow area after installation of the 'trench section into the excavation, (3) upright longitudinally extending side walls having their upper edges exposed, (4) an integral longitudinally ex- 9 tending upright divider separating the space between the side walls into two side-by-side raceways, respective transverse passageways extending the full width of each transverse foot, (6) knockout access means, one providing access for a utility line from one of the raceways to only one of the transverse passageways and the other providing access for a utility line from theother of the raceways to only the other of the transverse passageways,

a plurality of vertically removable, elongated cover sections of precast concrete having substantially planarupper surfaces resting on the upper edges of the side walls of the trench sections and butted together into end-to-end relation forming a continuous walkway on the upper surface thereof, each cover section further having l) longitudinal sides projecting a minor portion of their width laterally beyond the upright side walls of the trench sections and interfitting therewith to laterally position the cover sections, and (2) a longitudinally extending center portion cooperating with the divider means of each of the trench sections to separate the raceways and provide center support.

10. A utility trench system for undergrounding incompatibleutility lines, comprising:

an elongated one-piece, open-top base member of precast concrete having integral upright side walls, the base member to be buried in an excavation in theground with the upper edges thereof exposed,

open-top passageways formed in the based member extending transversely the width dimension thereof, each of the passageways having upright side walls of a height substantially less than the height of the upright side walls of the base member,

a removable, substantially planar slab of precast concrete extending the width and length of the base member and resting on the upper edges of the upright side walls of the passageways forming a bottom wall of an open-top trench defined by the upright side walls of the base member, the slab also having an integral divider extending upwardly from the bottom wall and parallel to the upright side walls of the base a distance approximating the height of the side walls of the base dividing the trench into two side-by-side raceways in which utility lines can be laid,

knockout access means in the bottom wall of the planar slab, one providing access for a utility line from one of the raceways to only one of the transverse passageways, and the other providing access for a utility line from the other of the raceways to only the other of the transverse passageways,

key means on the respective ends of the base member for locking the ends of like base members to form a continuous trench system, and

a vertically removable, elongated cover section of precast concrete having a substantially planar upper surface serving as a walkway resting on the upper edges of the side walls of the base member, whose longitudinal sides project a minor portion of their width laterally beyond the side walls of the base member and interfitting therewith to laterally position the cover section, the cover section also having a longitudinal center portion cooperating with the divider of the planar slab to separate the raceways and provide center support. 

1. A utility trench system for undergrounding incompatible utility lines which, for safety reasons and continued power maintenance, must not be laid in contact with each other or closely adjacent each other such that disruption of one line would result in breaking, short circuiting or otherwise disrupting the service of one or more of the remaining lines, comprising: a trench excavation in the ground, a plurality of elongated one-piece trench sections of precast concrete buried in the trench excavation and butted together in end-to-end relation forming a continuous length of open top side-by-side parallel raceways in which the incompatible utility lines are laid, with exit of the utility lines from one raceway to service locations available at intermittent points along the raceway through the bottom thereof without crossover or chance of contact with utility lines laid in the adjoining raceway, each trench section including (1) a base, (2) upright sidewalls integral with the base having their upper edges exposed at about ground level, (3) key means on the respective ends of each section for locking the ends of like trench sections together to prevent lateral and vertical shift relative to one another, (4) divider means of precast concrete mounted in the base dividing the trench into two separate sideby-side raceways for different utility lines, (5) two lateral passageways completely traversing the base at locations spaced longitudinally thereof and (6) knockout access means, one providing access for a utility line from one of the raceways to only one of the lateral passageways and the other providing access for a utility line from the other of the raceways to only the other of the lateral passageways; a plurality of vertically removable, elongated cover sections of precast concrete having substantially planar upper surfaces forming a continuous walkway, the cover sections butted together in end-to-end relation and resting on the upper edges of the upright sidewalls of the trench sections, each cover section further having (1) longitudinal sides projecting a minor portion of their width laterally beyond the upright side walls of the trench sections and interfitting therewith to laterally position the cover sections, and (2) a longitudinal center portion cooperating with the divider means of the trench sections to separate the raceways and provide center support.
 2. The trench system of claim 1 wherein each of the divider means of the trench sections provides support for the center portion of eAch cover when there is center deflection of the cover section responsive to unusually heavy loads.
 3. The trench system of claim 1 wherein each of the cover sections has three longitudinal ribs extending the length dimension thereof on the under surface, two of which rest on the upper edges of the upright side walls of the trench sections and the other of which cooperates with the divider means of the trench section.
 4. The trench system of claim 1 wherein the divider means of each trench section is integral with the base.
 5. The trench system of claim 1 wherein each of the lateral passageways of each trench section is adjacent to an end of the trench section, wherein the major part of the length of the base other than that occupied by the lateral passageways is of substantially reduced thickness, and wherein each trench section includes ground engaging side skirts extending downwardly from the upright side walls preventing settling of soil into the areas of reduced thickness after installation of the trench sections into the excavation.
 6. A utility trench system for undergrounding incompatible utility lines which, for safety reasons and continued power and maintenance, must not be laid in contact with each other or closely adjacent one another such that the disruption of one line would result in breaking, short circuiting or otherwise disrupting the service of one or more of the remaining utility lines, comprising: an elongated, one-piece base member of precast concrete having transverse feet at each end, ground engaging side skirts extending between each of the feet forming a hollow area beneath the base member and between the feet, the base member to be buried in an excavation in the ground with the upper edges thereof exposed, the ground engaging skirts preventing settling of soil into the hollow area after installation of the base member in the excavation, upright longitudinally extending side walls and a longitudinally extending upright divider separating the space between the side walls into side-by-side raceways, respective transverse passageways extending the full width of each foot, knockout access means, one providing access for a utility line from one of the raceways to only one of the transverse passageways and the other providing access for a utility line from the other of said raceways to only the other of the transverse passageways, and a vertically removable, elongated cover section of precast concrete having a planar upper surface functioning as a sidewalk and resting on the upper edges of the side walls, the longitudinal sides of the cover section projecting a minor portion of their width laterally beyond the upright side walls of the base member and interfitting therewith to laterally position the cover section, the cover section also having a longitudinally extending center portion cooperating with the divider means of the base member to separate the raceways and provide center support.
 7. The utility trench system of claim 6 wherein the cover section has three longitudinally extending ribs on the under surface thereof, two of which rest on the upper edges of the side walls of the base member and the other of which cooperates with the divider means.
 8. The trench system of claim 6 wherein the top edges of the side walls of the base member include notches and wherein the longitudinal ribs of the cover section resting on the side walls have complementary integrally formed projections interfitting with the notches in the side walls preventing longitudinal movement of the cover section when in place.
 9. A utility trench system for undergrounding utility lines which, for safety reasons and continued power maintenance, must not be laid in contact with each other or closely adjacent each other such that disruption of one line would result in breaking, short circuiting or otherwise disrupting the service of one or more of the remaining utility lines, comprising: a trench excavation in the ground, a pluralitY of elongated one-piece trench sections of precast concrete butted together in end-to-end relation forming continuous parallel raceways in which the incompatible utility lines are laid, with exit of the utility lines in each raceway to service locations available at intermittent points along the raceway through the base of the trench section without crossover or chance of contact with utility lines laid in the adjoining raceway, each trench section including (1) an elongated, onepiece base member of precast concrete having transverse feet at each end and having a hollow portion between the transverse feet, (2) ground engaging side skirts between each of the feet preventing settling of the soil into the hollow area after installation of the trench section into the excavation, (3) upright longitudinally extending side walls having their upper edges exposed, (4) an integral longitudinally extending upright divider separating the space between the side walls into two side-by-side raceways, (5) respective transverse passageways extending the full width of each transverse foot, (6) knockout access means, one providing access for a utility line from one of the raceways to only one of the transverse passageways and the other providing access for a utility line from the other of the raceways to only the other of the transverse passageways, a plurality of vertically removable, elongated cover sections of precast concrete having substantially planar upper surfaces resting on the upper edges of the side walls of the trench sections and butted together into end-to-end relation forming a continuous walkway on the upper surface thereof, each cover section further having (1) longitudinal sides projecting a minor portion of their width laterally beyond the upright side walls of the trench sections and interfitting therewith to laterally position the cover sections, and (2) a longitudinally extending center portion cooperating with the divider means of each of the trench sections to separate the raceways and provide center support.
 10. A utility trench system for undergrounding incompatible utility lines, comprising: an elongated one-piece, open-top base member of precast concrete having integral upright side walls, the base member to be buried in an excavation in the ground with the upper edges thereof exposed, open-top passageways formed in the based member extending transversely the width dimension thereof, each of the passageways having upright side walls of a height substantially less than the height of the upright side walls of the base member, a removable, substantially planar slab of precast concrete extending the width and length of the base member and resting on the upper edges of the upright side walls of the passageways forming a bottom wall of an open-top trench defined by the upright side walls of the base member, the slab also having an integral divider extending upwardly from the bottom wall and parallel to the upright side walls of the base a distance approximating the height of the side walls of the base dividing the trench into two side-by-side raceways in which utility lines can be laid, knockout access means in the bottom wall of the planar slab, one providing access for a utility line from one of the raceways to only one of the transverse passageways, and the other providing access for a utility line from the other of the raceways to only the other of the transverse passageways, key means on the respective ends of the base member for locking the ends of like base members to form a continuous trench system, and a vertically removable, elongated cover section of precast concrete having a substantially planar upper surface serving as a walkway resting on the upper edges of the side walls of the base member, whose longitudinal sides project a minor portion of their width laterally beyond the side walls of the base member and interfitting therewith to laterally position the cover section, the coveR section also having a longitudinal center portion cooperating with the divider of the planar slab to separate the raceways and provide center support. 